Yarn inspector



Dec. 1, 1970 R. B. FERTIG 3,543,369

YARN INSPECTOR Filed Dec. 13, 196e y 5 sheets-sheet 1 INV ENTOR QAYMoNo Bmuas FER-vm mfggim, oewm ATTORNEYS l R. B. FERTIG 3,543,360

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ATTORNEYS Dec. l, 1970 R, B FERTlG 3,543,360

YARN INSPECTOR Filed Dec. 1s, 196s 5 sheets-sheet 4 Dec. l, 1970 R. B. FERTIG YARN INSPECTOR Filed Dec. 13, 1968 5 Sheets-Sheet 5 i A g United States Patent O' U.S. Cl. 28-51 28 Claims ABSTRACT OF THE DISCLOSURE A yarn inspector for detecting slub-like defects in a yarn sheet, including a light source projecting a narrow beam across the sheet, through which the sheet passes and a photodetector. The signals from the photodetector are routed through a major defects channel, a minor defects channel, and a length channel, each of which have a variable gain amplifier with a feedback loop including a variable resistance unit producing linear change of resistance and gain with movement thereof to set the sensitivity level of the respective channel. The length channel measures the number of defects per selected length increment of the yarn sheet, the yarn sheet length being measured by sensing travel of the yarn sheet.

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to yarn inspection apparatus for continuously monitoring a large group of yarns arranged to move substantially in unison in sideby-side relation in a feed plane, which are commonly referred to as a yarn sheet, and detecting occurrence of defects in the yarns making up the yarn sheet and producing a defect signal.

Feeding of yarns in large groups as yarn sheets occurs in many different types of yarn handling apparatus, such as in knitting machines, particularly of the tricot or warp knitting machine type, in weaving machines or looms, in feeding of yarns from the creel of a warping machine or to the beams of knitting machines, and in similar yarn making and textile manufacturing devices. Immediate detection of defects in the yarns making up the yarn sheet, such as slubs, stripbacks, and broken filaments in multi-filament yarn, is particularly important for a number of reasons, such as to avoid costly waste from production of defective fabric by the knitting machine or loom into which the yarns are being fed.

Photoelectric yarn inspectors have heretofore been developed for automatically inspecting such yarn sheets as the yarns move along the feed path, for example, during the beaming process, lby directing the yarns across two guide bars which transversely span and underlie the yarn feed path, directing a light beam transversely across the yarn sheet so that a certain amount of the light beam is intercepted 'by the yarn sheet, and detecting the intensity of the light received at the opposite side edge of the yarn sheet from the edge adjacent which the light source is located.

ln the past, such yarn inspectors have generally performed three functions. They have detected major defects and stopped the warper upon such detection, they have detected minor defects and counted them, without stopping the warper, and they have sensed the length of a long defect or a series of defects. The major and minor defect detecting channels have been identical, the only difference being in the settings of the sensitivity controls, the minor defect control being set at a higher setting than the major defect control. Minor defects are detected by 'both channels. For example, if a 1% defect were detected at a sensitivity control setting of 100, then a 3,543,360 Patented Dec. l, 1970 2% defect should produce asignal twice as large in amplitude and be detected at a setting of 50 assuming a linear control. Larger flaws are detected at lower settings which become closely spaced, for example, a 10% defect at a setting of 10 and a 12% defect at a setting of 8.3. A high and a low sensitivity switch is sometimes provided to help alleviate this diculty. However, this has been recognized as objectionable since it is very easy for the operator to place the switch in the wrong position and thus be operating with the wrong -sensitivity setting which can either provide very little detection or too many false stops. The sensitivity control normally has a 0-100 calibration. A setting of 50 on the major channel is not necessarily the same as a setting of 50 on the minor channel. Settings of two units would not likely be the same for equal detection sensitivities. Thus, each channel of each instrument had to be calibrated with a special pulse generator which was both a tedious and time-consummg operation.

Also, in the length mode of operation of conventional yarn inspectors, the controls had to be reset every time the speed of the beamer was changed and the controls were not direct reading or accurate. In fact, the setting of the length controls 4when the speed of the beamer was changed was a diicult trial and error operation in the field, and settings dilfered from unit to unit.

Defect size, linearity, -and uniformity, are properties which are of considerable importance in photo-electric yarn inspectors. Defect size is normally considered to be that percentage of the total light transmitted which the defect blocks off from the detector head. For example, a 10% defect blocks oif 10% of the light that the detector head normally receives. Linearity means that a 10% defect will block olf ten times as much light as a 1% defect and thus generate a signal ten times as large. Uniformity across the yarn sheet means that a defect of a given size will generate a signal of the same amplitude no matter where the defect is located transversely of the yarn sheet, that is, whether near either end or in the middle.

An object of the present invention is the provision of a novel improved yarn inspector for photo-electrically inspecting sheets, which provides improved linearity and uniformity of sensitivity across the yarn sheet.

Another object of the present invention is the provision of a novel improved photoelectric yarn inspector for inspecting yarn sheets as the yarns pass along their feed path, which has a direct reading linear defect size control and automatic speed compensation and is capable of detecting either the number of defects or the total length of defects per selected length.

Other objects, advantages and capabilities of the present invention will become apparent from the ensuing detailed description of a preferred embodiment, taken in conjunction with the accompanying drawings.

The yarn inspector of the present invention, which is described as an illustrated example of a yarn inspector to be disposed between a creel and a beamer, employs the conventional pair of transverse precision guide bars over which the yarn sheet is passed, with a light source adjacent one edge of lthe yarn sheet and a detector head assembly adjacent the other edge, together with an optical system to produce an accurately collimated light beam which is intercepted by the yarn sheet. Improved sensitivity regulation is attained in the yarn inspector of the present invention by providing a direct reading defect size control, which is normally supplied as a rotary tap switch but can be supplied as a continuous control if desired, using a linear resistance change to regulate defect size control and operational amplifier techniques along with precision resistors in feedback loops to obtain accurate sensitivity settings which are reproducible not only from channel to channel but from unit to unit and which will remain accurate over long periods of time. The present apparatus also uses a photoelectric-type pulse generator attached to a measuring roll over which the yarn sheet is drawn to the beamer to provide accurate length signals and automatic speed compensation. This enables the unit to be accurately calibrated in the length mode of operation and to be reproducible from unit to unit. In addition, it is direct reading and requires no charts or guess work in making the settings. Since the speed control automatically varies with changes in beamer speed, of course no changes in the setting are necessary when the speed of the beamer is changed.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a side elevation View of a yarn inspector embodying the present invention, as viewed from the location of the line 1-1 of FIG. 2 between the yarn inspector and the beamer;

FIG. 2 is an end elevation view of the yarn inspector, with parts of the upper portion thereof shown in section, and with a warp beam indicated diagrammatically;

FIG. 3 is a simplified block diagram of the yarn inspector circuitry;

FIG. 4 is a schematic diagram of the amplifier, comparator, and defect size control circuitry;

FIG. 5 is a more detailed diagram of the length measuring circuitry of the yarn inspector designed to count defects per selected length;

FIG. 6 is a more detailed diagram of the length measuring circuitry designed to measure the length of the defects, with some parts shown schematically;

FIG. 7 is a schematic diagram of the number of defects counter including the decoder; and

FIG. 8 is a diagram of the optical system employed in the yarn inspector.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, and particularly to FIGS. 1 and 2, there is shown a yarn sheet, generally indicated by the reference charcter 10, extending between the creel (not shown), and a beamer, diagrammatically indicated at 11. The yarn inspector of the present invention, generally indicated by the reference character 12, is stationed between the creel and the beamer and comprises a rectangular cross-section tubular supporting beam 13 transversely spanning and underlying the yarn sheet 10, supported by shock mounts 14 on two adjustable, vertically extending stanchions 15, all of conventional construction. Securely mounted on top of the rectangular beam 13 are a pair of precision guide bars 16, over the uppermost surface portion of which the yarns forming the yarn sheet pass, the guide bars serving to precisely locate the yarns in a selected horizontal plane in the region between the guide bars. A light source head 17, diagrammatically illustrated in FIG. 8, is mounted at one end of the rectangular beam 13 adjacent one lateral edge of the yarn sheet, and comprises, for example, a lamp 18, a bi-concave lens 19, a plano-convex lens 20, and an apertured mask 21 having a circular aperture therein, and a glass window 22 arranged along an optical axis within a suitable housing to direct a highly collimated beam of light transversely across the path of the yarn sheet. Mounted on the other end of the rectangular beam 13 is a detector head 23, for example, having a glass Window 24, a mask 25 having a rectangular aperture therein, a plano-convex lens 26, and a phototransistor 27 therein arranged to receive the light beam directed across the yarn sheet path from the light source head 17 and produce an output signal from the phototransistor which is proportional to the intensity of the light received, and therefore varies in determinable 4 relation to the proportion of the light beam blocked by the yarns and any yarn defects in the light beam.

As is illustrated in FIG. 1, the yarns coming from the creel pass along converging paths through an eye board 28, and then pass beneath a hold-down rod 29 and through a reed 30, both supported at their opposite edges outwardly of the lateral edges of the yarn sheet 10 by vertical support members extending from the shock mount 14. After passing the yarns through the reed 30, they extend in overlying engagement with the uppermost surface portions of the yarn guide bars 16, which locates them in a horizontal plane in alignment with the optical axis of the collimated light beam between the light source head 17 and detector head 23. After passage through the light beam, the yarns extend over a measuring roll 31 which is rotated in accordance with the speed of travel of the yarns by frictional engagement therewith, and then wind upon the beam 11 of the beamer. The electrical circuitry of the yarn inspector includes an amplifier housing 32 and relay housing 33, both fixed on one of the stanchions 15, a pulse generator 34 associated with the measuring roll 31, and a counter housing 35 electrically coupled to the pulse generator 34 and to the amplifier housing 32.

Referring to FIG. 3, there is shown a simplified block diagram of the yarn inspector circuitry, with some circuit components shown schematically to facilitate a simplified description of the electrical operation of the device. The detail schematic circuits of the circuitry illustrated generally in FIG. 3 are shown in FIGS. 4, 5, 6 and 7. The yarn inspector circuitry, as indicated in FIG. 3, employs three channels, channel 36 for major defects, channel 37 for minor defects, and channel 38 having a length function. The major channel 36 is usually set with only enough sensitivity to pick up the larger defects, count these defects, and stop the beamer 11 so they may be removed. The minor defects channel 37 is usually set at a higher sensitivity and detects small defects as well as the larger ones. However, channel 37 usually only counts these defects and does not stop the beamer. The length channel 38 counts defects as a function of length and may be set to stop the beamer if desired.

The detector head 23, upon detection of a defect, gencrates a negative pulse proportional to the size of the defect. This negative pulse is applied along branched lead 39 to the inputs of each of the channels 36, 37 and 38. The negative pulse applied to the major defects channel 36 is coupled through capacitor 36-C1, which may be a set of capacitors associated with a selector switch as later described, and through resistor 36R1 to the input of an operational amplifier 36-A which has a voltage divider consisting of a step switch type variable resistor unit 36-R3, indicated for simplicity as a potentiometer, and resistor S16-R4 across its output.

A feedback resistor 36-R2 is connected from the slider of the variable resistance unit 36-R3 to the input of the amplifier 36-A. The ratio of 36-R2 to 36-R1 and the setting of resistance unit 36-R3 determines the gain of the amplifier 36-A which is highest in the CCW position and lowest in the CW position. This feedback arrangement enables the instrument to be easily calibrated directly in defect size and will be described in detail later.

The output of the operation amplifier 36-A, a positive pulse, is fed through resistor 36-R7 to the input of comparator 36-B which is simply another operational amplifier without negative feedback. A reference voltage of one volt negative from the voltage divider consisting of resistors 36-R9 and 36-R10 is also fed through resistor 36-R8 to the input of the comparator 36-B. If the positive output pulse of amplifier 36-A is higher than the one volt reference voltage, the comparator 36-B switches from a positive output voltage of about ten volts to a negative voltage of about the same amplitude. It stays in this state until the input voltage drops to a voltage slightly lower than the reference voltage. There is a resistor 36-R11 from the output of the comparator 36-B to a voltage divider consisting of resistors 36-R5 and 36-R6 on the input. This is a positive feedback arrangement which improves the switching action of the comparator 36-B, making it more snap acting. The negative output pulse from the comparator 36-'B is coupled by capacitor 36-C2 to a one-shot multivibrator 36-D which produces an output pulse having a duration of about 50 milli-seconds, which is fed to the counter driver amplifier 36-E and is suiciently long to actuate the major counter 36-F. The output pulse of the counter driver 36-E actuates the major counter B16-'F which is of the electro-mechanical type. The output of the counter driver amplifier 36-E is connected to the movable contact 40a of stop motion switch 40-SW, and if this switch is in the IN service position, a signal is applied to the OR gate 41 which in turn feeds a relay driver amplifier 42. This actuates the control relay REI which is used to stop the beamer 11.

The circuitry and operation of the minor channel 37 is identical to the major channel 36, except that the defect size variable resistance unit 'S7-R3 (not shown) is set for a smaller defect size than is the major channel and the stop motion switch contact 4Gb (not shown) is usually set in the OUT of service position. The beamer is not stopped but the minor channel counter 37-F is actuated.

In the length mode of operation, conventional yarn inspectors usually convert the defect signal into a rectangular pulse of constant amplitude and integrate these pulses by means of an R-C circuit in order to produce a signal more or less proportional to the duration of a single defect or series defect signals. Obviously, such a system depends upon the speed of the warper and has to be adjusted every time the speed of the warper is changed. Since the integrating capacitor has a discharge path, the spacing of the defect signals influences the output voltage of the integrator and makes adjustment of the circuit uncertain and a compromise at best.

In the present system, an entirely different approach is used. A pulse generator 34 which generates 120 pulses per revolution is attached to the measuring roll 31 of the beamer 11. This roll 31 is usually l2 inches in circumference which makes each pulse from the pulse generator 34 equal to .1 inch and suitable for decade counters. If the measuring roll 31 is of a different circumference, suitable gearing is used to make each pulse equal to .l inch. The use of the pulse generator in this manner, gives the system an accurate measurement of length at all times regardless of beamer speed and permits use of a direct reading (inches) length selector switch.

It is believed that most users of yarn inspectors are more interested in the number of defects per selected length rather than the actual length of these defects. Accordingly, the length channel 38 of the present system will normally be designed to measure the number of defects per selected length. In such a length channel 38, the defect pulse is amplified by operational amplifier 38A and compared by comparator 38-B as in the maljor channel 36. However, the output of the comparator 38-B is fed into two counter circuits 43 and 44. The selected length counter circuitry 43 removes the reset voltage from both counters 43 and 44 which permits both counters to operate. The lower counter 43 measures the length of the yarn to be monitored after a defect is detected by counting the pulses from the pulse generator 34. This length is selected by a switch (not shown) which causes both counters to be reset if the number of defects as selected by the switch for the upper number of defects counter 44 is not reached first. If the selected number of defects is reached, a negative pulse is fed to the one-shot multivibrator 38-D which in turn operates the counter driver 38-E and length counter 38-F. If the contact 40C of stop motion switch 40-SW is in the IN service position, the beamer 11 is stopped. A more detailed description of the length circuitry will be given later.

The detailed schematic circuit of the major defect channel 36 is shown in FIG. 4. Referring to FIG. 4, wherein a representative schematic circuit including the phototransistor 23-Q1 for the detector head 23 is also illustrated, the negative pulse from the detector head 23 is coupled by capacitor 36-C1A to resistor 36-R1 which connects to the input of the operational amplifier 'S6-A. 36-SW1 is a low frequency cutoff switch which selects one of three capacitors 36-C1A, 36-C1B, or 36-C1C, the size of which determines the low frequency response of the amplifier 36-A. It is desirable to have maximum low frequency response but noise from movement of the yarn sheet usually prevents use of the lowest frequency position of the switch unless the defect size control is set to pick up a fairly large defect. After the signal passes through the amplifier 36-A, it is inverted and applied to the base of transistor 36-Q1 which is connected as an emitter follower and serves to boost the current handling ability of the amplifier 36-A as a rather low value load is connected to its output. The output of 36-Q1 is connected to a voltage divider forming the variable resistance unit 36-R3 and resistor 36-R4 and consisting of resistors 36-R3A to 36-R3K and 36-R4. The feedback resistor 36-R2 is connected to the top of 36-R3K which is the 12% defect size by switch 36-SW2. In this position, the gain of the amplifier 36-A is determined by the ratio of 36-R2 to 36-R1 which is 1.666. A 100% defect signal produces a 5 volt pulse, so a 12% defect will produce a 600 mv. signal. Therefore, the gain ratio of 1.666 times the 600 mv. signal equals l volt, which is the desired output level of the amplifier. By the same reasoning, a 1% defect signal will produce 50 mv., which will require a gain of twenty. This is the gain of the amplifier 36-A lwhen the feedback resistor 36-R2 is connected to the lower end contact RSA of resistance unit 36-R3. The output voltage divider 36R3 increases the gain of the amplifier 36-A by a factor of twelve in the 1% position.

A zero control B16-R13 is provided for bucking out the small off set voltage present at the input of the amplifier 36-A. It is part of a voltage divider consisting of 36-R12, J.i6-R13, and 36-R14 between the +15 v. DC and l5 v. DC power supplies. This lbucking voltage is applied to the input of the amplier 36-A by resistor S16-R21. Capacitor 36-C4 across resistor 36-R2 serves to limit the high frequency response of the amplifier to eliminate any high frequency noise signals. Capacitor 36-C3 is the frequency compensating capacitor for the amplifier to prevent oscillation. The values of the capacitors indicated in the drawings are in micro-farads unless otherwise given. Resistors 36-R16 and 36-R18 are current limiting resistors for the amplifier 36-A and transistor 36-Q1.

The positive output pulse of 36-Q1 is connected to the input of comparator 36-13 by resistor 36-R7 where it is compared with precisely one volt negative from a voltage divider consisting of resistors 36-R9 and 36-R10. This reference voltage is connected to the input of the comparator by resistor 36R8. If the output of 36-Q1 is slightly greater than one volt, the comparator 36-B which has very high gain will switch from a negative voltage of about ten volts at the output of a positive voltage of about the same magnitude. Resisor 36-R11 and voltage divider 36-R6 and 36-R5 form a positive feedback loop for improving the switching action of the comparator.

It will be apparent, therefore, that the sensitivity control of the amplifier channel to effect selection of defect size upon adjustment of the selector switch 36$W2 uses a negative feedback loop formed by the resistor 36-R2 and a voltage divider formed of resistors 36-R3A to 36-R3K and 36-R4 across the output of the amplifier 36-A. The gain of the amplifier is determined by the feedback ratio and the ratio of the voltage divider tap to the total divider resistance, neglecting the loading effect of the feedback resistor which is very small. The accuracy of the defect size settings of the switch 36-SW2 is determined primarily by the tolerances of the feedback resistor and the voltage divider resistors, which are 1% units, because of the feedback arrangement and the high gain operational amplifier 36-A. The resistance values used in the voltage divider are linear with defect size but vary the gain in an inverse linear fashion. Of course, a linear potentiometer may be substituted for the step switch type voltage divider and its rotation will be linear in relation to defect size.

The schematic circuit for the minor defects channel 37 is identical to that of the major defects channel 36, the setting of the switch of channel 37 corresponding to the switch 36-SW2 of the channel 36 being for a smaller defect size, and the stop motion switch contact 40h being normally set in the OUT of service position. Also, the schematic circuit for the stages of the length function channel 38 up through the comparator 38B is the same as that for the other two channels.

FIG. 5 illustrates the schematic circuit for the two counter circuits 43 and 44 of the length channel 38 when designed to count defects per selected length. Referring to FIG. 5, after a defect is picked up by the detector head 23, the length comparator 38-B puts out a positive pulse of about 10 volts. This pulse is applied to a voltage divider consisting of resistors 43-R25 and 43-R26 which reduces this voltage to a level suitable for NOR gates employed in the circuit. The pulse appearing at the junction of resistors 43-R25 and 43-R26 is applied to one input of a NOR gate 43-G1 which causes its output to go to the high state. The output of the first NOR gate 43-G1 is applied to one input of the second NOR gate 43-G2 which causes it to go to the low state. The output of the second NOR gate 43-G2 is connected to the other input of the first NOR gate 43-G1. This results in cross coupled NOR gates or a LATCH circuit 43-L. It will stay in this position until a positive pulse is applied to the other input of the second NOR gate 43-G2. Diode 43-CR1 is used to protect the first NOR gate 43-G1 from the high negative voltage normally present at the output of the comparator 38-B.

The low output of the first NOR gate 43-G1 is applied to the base of the transistor 43-Q2` which causes it to cut off. This removes the voltage from across resistor 43-R27 in the emitter of 43-Q2, also, the reset voltage from all decade counters 43-H1 to 43-H3 and 44-H1 (which, for example, are type 9958 decade counters),

both in the length counter 43 and the number of defects counter 44. All their decade counters are now reset and ready to start counting. Resistor 43-R3-2 is a current limiting resistor in the reset circuit of the three decade counters 43-H1 to f3-H3` in the length counter 43.

The pulse generator 34, which is preferably a photoelectric type putting out ten pulses for each inch of yarn is generating positive pulses of about ten volts all the time the beamer 11 is running. These pulses are applied to a voltage divider consisting of resistors 43-R30 and 43 R31 which reduces this voltage to a level suitable for the first decade counter 43-H1. These pulses are counted by the three decade counters 43-H1, 43-H2, and 43-H3. The output of the third decade counter 43-H3 in binary form, using the 8, 4, 2, l code, is fed to buffer circuit 43-1 (preferably a type MC846P buffer) which consists of four inverting amplifier stages, one for each output of the decade counter. As the count signal from the decade counter 43-H3 is in the low state, the count signal from the buffer 43-I is in the high state. The output of the buffer circuit 43-1 is fed to a decoder 4S which changes the binary input signals to decimal output signals. Length selector switch 43-SW is shown in the ten inch position. After ten inches has been measured by the pulse generator 34, a positive pulse is generated by the decoder 45. This positive pulse is applied through capacitor 43-C9 to resistor 43-R29 and one input of the two NOR gates 43- G3 and 43-G4 connected as a ONE SHOT multivibrator 43-1. The positive output pulse of the ONE SHOT 43-I is coupled to the other input of the NOR gate 43-G2 in the LATCH circuit 43-L. Resistor 43-R28 and capacitor 43 C6 forrn the timing circuit for the ONE SHOT multivibrator. This causes the LATCH circuit 43-L to go back to its original state, applying a reset signal to all decade counters and stopping them from counting. Transistor 43- Q3 is actuated by the ONE SHOT 43-1 and is a shunt switch across the input of the LATCH circuit 43-L and serves to remove any signals from the comparator 3'8-B which might prevent the LATCH circuit and decade counters from being reset. The length counter 43 is now ready to be actuated by the next defect signal from the comparator 38-B.

At the same time the first defect signal from the length comparator 38-B removed the reset signal from all decade counters, it was also applied to the voltage divider consisting of resistors 44-R33 and 44-R34, which has the same function as the other voltage divider t3-R25, #f3-R26, previously described. The pulse from the voltage divider 44-R33, 44-R34, is applied to the input of the decade counter 44-H1 in the defect counter circuit 44. Each defect occurring during the ten inch measuring period is also applied to this counter 44-H1. The output of the counter 44-H1 is applied to another buifer circuit 44I and decoder 46 which operate exactly the same as those in the length counter. Since the selector switch 44-SW is shown in the two defects position, the second defect would result in an output pulse which would trigger the one shot multivibrator 38-D ahead of the counter driver 38-E (FIG. 3). This would actuate the mechanical counter 38-F and stop the beamer 11 if the contact c of stop motion switch 40-SW was in the IN service position. If only one defect occurs during the ten inch counting period, the length counter 43 resets all decade counters and there is no actuation of the mechanical counter and stoppage of the beamer.

FIG. 6 illustrates schematically the optional length measuring system, wherein the same length counter 43 is used, and therefore is indicated only as a phantom line block in this figure, but the number of defects counter 44 is replaced by a counter 47 which measures the length of the defects. A negative pulse from the comparator 38-B cuts off shunt switch 47-Q4 and allows pulses from the pulse generator 34 to enter the two decade counters 47-H1 and 47-H2. These pulses are counted, buffered, and decoded as described for the number of defects counter 44. Since selector switch 47-SW is shown in the one inch position, a defect one inch long (ten pulses) would result in an output pulse from the decoder 48. This would result in actuation of the mechanical counter 38-F and the beamer 11 being stopped if contact c of the stop motion switch 40SW was in the IN service position.

The same thing would happen if two defects '1/2" long actuated the comparator 38-B. The only difference would be two actuations of the comparator 38-B and shunt switch 47-Q4. 47-Q4 only permits pulse generator signals to get to the decade counters 47-H1 and 47-H2 while the comparator 38-B is actuated by a defect signal. In this way the length of defect counter 47 measures the length of one or more defects.

FIG. 7 is a schematic diagram of portions of the number of defects counter 44 including the decoder 46. The decade counter 44-H1, when reset, has all outputs, pins 2, 3, 4 and 5, in the high state. When one defect enters the counter, pin 5, the l output, goes low. Two' inputs drive pin 4, the 2 output, low and raise the 1 output to high. Three inputs cause the l output to go back to low and the 2 output remains low. Other input signals operate the counter in a similar fashion.

The buffer 44-1 inverts the outputs of the decade counter 44-H1 and causes the low output signals to be high output signals from the buffer. A three count in the buffer would result in pins 3 and 6 being high.

The decoder 46 used with the counters is a very simple diode decoder and operates as follows:

For a count of one, the 3 terminal of the buffer 44-1 would be high and no decoding is necessary. 'It is connected directly to the l position of 44-SW. For a count of two, the 6 terminal would be high and connected directly to the 2 position of 44-SW. For a count of 3, pins 3 and 6 would be high. Diode 46-CR4 is connected to the 1 output and diode 46-CR5 is connected to the 2 output. The anode end of these diodes is connected to a resistor 46-R40, the other end of which is connected to +5 v. DC. Since on a count of 3, the 1 and 2 outputs of the buffer 44I are high, 46-CR4 and 46-CR5 are back biased and the anodes of these diodes go to the high state which is connected to the 3 position of 44-SW. If the 1 output was low, current would fiow through 46-CR4 and the anodes of 46-CR4 and 46-CR5 would be low. The decoder 46 operates in a similar fashion in the rest of the switch positions.

I claim:

1. Yarn inspection apparatus for detecting slub-like defects in yarns forming a yarn sheet of plural substantially parallel yarns moving in a selected feed plane, comprising light source means located outwardly adjacent one edge of the yarn sheet for projecting light transversely across the yarn sheet in a narrow beam through which the yarns move, photodetector means located outwardly adjacent the opposite edge of the yarn sheet in the path of said beam for sensing said beam and producing output detector signals whose amplitudes vary as a function of variations in the luminous intensity of the beam, circuit control means coupled to said photodetector means for processing said detector signals and counting the number of defects signified thereby above a selected threshold size responsive to the amplitudes of the detector signals, comprising amplifier channel means including a first amplifier channel having a variable gain amplifier and a feedback loop coupling output signals from said amplifier is feedback signals to the input thereof for regulating the gain of said amplifier, said feedback loop including variable resistance means to which said output signals are applied forming a defect size control regulating the feedback signal level applied to said input and a manually adjustable member for changing the electrical resistance of said resistance means and the feedback signal level in linear relation to movement thereof to thereby vary the gain of said amplifier in inverse linear relation to the changes in said electrical resistance, defect counter means, and activating means coupled to the output of said amplifier for activating said counter means to record a defect count responsive to each of output signals from said amplifier which exceeds a selected signal level signifying a selected defect size range.

2. Yarn inspection apparatus as defined in claim 1, wherein said variable resistance means is a plurality of series connected resistor sections of like value having switch tap members connected to junctions between the respective resistor sections thereof, and said manually adjustable member is a movable switch contact selectively engageable with said tap members for applying feedback signals therefrom to the input of said amplifier.

3. Yarn inspection apparatus as defined in claim 1, wherein said variable resistance means is a plurality of series connected resistor sections of like value having switch tap members connected to junctions between the respective resistor sections thereof, and said manually adjustable member is a movable switch contact selectively engageable with said tap members for applying feedback signals therefrom to the input of said amplifier, said tap members being calibrated in linearly ascending defect size percentages in steps of one percent.

4. Yarn inspecting apparatus as defined in claim 2, including a first fixed resistor between said photodetector means in the input of said amplifier, and said feedback loop including a second fixed resistor connected between said input and said switch contact, the ratio of the resistance values of said first and second resistors establishing a first selected gain for said amplifier when said switch contact engages the highest order tap member of said resistance means and collectively with said resistor sections establishing gains for said amplifier which increase linearly upon engagement of said contact with progressively lower order tap members.

5. Yarn inspecting apparatus as defined in claim 3, including a first fixed resistor between said photodetector means in the input of said amplifier, and said feedback loop including a second fixed resistor connected between said input and said switch contact, the ratio of the resistance values of said first and second resistors establishing a first selected gain for said amplifier when said switch contact engages the highest order tap member of said resistance means and collectively with said resistor sections establishing gains for said amplifier which increase linearly upon engagement of said contact with progressively lower order tap members.

6. Yarn inspecting apparatus as defined in claim 1, wherein said activating means comprises a comparator connected to the output of said amplifier having first and second states responsive to amplified output signals levels respectively below and above a selected value, and counter driver means responsive to occurrences of said second state for actuating said counter to record a count.

7. Yarn inspecting apparatus as defined in claim 2, wherein said activating means comprises a comparator connected to the output of said amplifier having first and second states responsive to amplified output signals levels respectively below and above a selected Value, and counter driver means responsive to occurrences of said second state for actuating said counter to record a count.

8. Yarn inspecting apparatus as defined in claim 3, wherein said activating means comprises a comparator connected to the output of said amplifier having first and second states responsive to amplified output signals levels respectively below and above a selected value, and counter driver means responsive to occurrences of said second state for actuating said counter to record a count.

9. Yarn inspecting apparatus as defined in claim 4, wherein said activating means comprises a comparator connected to the output of said amplifier having first and second states responsive to amplified output signals levels respectively below and above a selected value, and counter driver means responsive to occurrences of said second state for actuating said counter to record a count.

10. Yarn inspecting apparatus as defined in claim 1, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means having first and second positions for respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to conditioning of said acltil'/ating means to activate the counter associated there- Wlt 11. Yarn inspecting apparatus as defined in claim 2, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means having first and second positions for respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to `conditioning of said actilyating means to activate the counter associated therewit 12. Yarn inspecting apparatus as defined in claim 3, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means having first and second positions for respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to conditioning of said l 1 activating means to activate the counter associated therewith.

13. Yarn inspecting apparatus as defined in claim 4, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means having first and second positions for respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to conditioning of said activating means to activate the counter associated therewith.

14. Yarn inspecting apparatus as defined in claim 6, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means having first and second positions for respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to conditioning of said activating means to activate the counter associated therewith.

15. Yarn inspecting apparatus as defined in claim 1, including a second amplifier channel having a variable gain amplifier, a feedback loop, activating means and a counter like the corresponding elements of said first channel and means for adjusting the feedback loops of said channels to different gain control levels whereby said first and second channels respectively form a major defects channel for counting larger size defects in said first channel and a minor defects channel for counting smaller size defects in said second channel.

16. Yarn inspecting apparatus as defined in claim 2, including a second amplifier channel having a variable gain amplifier, a feedback loop, activating means and a counter like the corresponding elements of said first channel and means for adjusting the feedback loops of said channels to different gain control levels whereby said first and second channels respectively form a major defects channel for counting larger size defects in said first channel and a minor defects channel for counting smaller size defects in said second channel.

17. Yarn inspecting apparatus as defined in claim 3, including a second amplifier channel having a variable gain amplifier, a feedback loop, activating means and a counter like the corresponding elements of said first channel and means for adjusting the feedback loops of said channels to different gain control levels whereby said first and second channels respectively form a major defects channel for counting larger size defects in said first channel and a minor defects channel for counting smaller size defects in said second channel.

18. Yarn inspecting apparatus as defined in claim 15, including relay means for stopping feeding of the yarn sheet along said path, and switch means between said relay means and said activating means of each of said channels hving first and second positions respectively connecting and disconnecting said relay means therewith to selectively produce activation of said relay responsive to conditioning of said activating means to activate the counter associated therewith.

19. Yarn inspecting apparatus as defined in claim 1, including a measuring roll and pulse generator means activated by contact with the yarns of said yarn sheet to produce pulses whose number is a measure of the travel of the yarn sheet, a second variable gain amplifier and feedback loop like said first-mentioned variable gain aniplifier and feedback loop for receiving said detector signals, length function circuit means responsive to said pulses and to output signals from said second amplifier for counting the number of defects of selected size in the yarn passing through said beam during each selected length increment of the yarn sheet, and means for indicating occurrence of a selected number of defects counted by said length function circuit means during each said selected length increment.

20. Yarn inspecting apparatus as defined in claim 19,

wherein said length function circuit means comprises first counter means responsive to said output signals for counting the number of defects signified by said output signals between successive resettings of said first counter means, and second counter means responsive to said pulses to count the same and reset said first counter means upon occurrence of a selected pulse count.

21. Yarn inspecting apparatus as defined in claim 19, including relay means for stopping feeding of the yarn sheet along said path, and switch means selectively connecting said relay means with said length function circuit means having a first position disconnecting said relay means therefrom and a second position connecting the relay means therewith to activate the latter when the number of defects counted during any of said selected length increments exceeds a selected count level.

22. Yarn inspecting apparatus as defined in claim 20, including relay means for stopping feeding of the yarn sheet along said path, and switch means selectively connecting said relay means with said length function circuit means having a rst position disconnecting said relay means therefrom and a second position connecting the relay means therewith to activate the latter when the number of defects counted during any of said selected length increments exceeds a selected count level.

23. Yarn inspection apparatus for detecting slub-like defects in yarns forming a yarn sheet of plural substantially parallel yarns moving in a selected feed plane, comprising light source means located outwardly adjacent one edge of the yarn sheet for projecting light transversely across the yarn sheet in a narrow beam through which the yarns move, photodetector means located outwardly adjacent the opposite edge of the yarn sheet in the path of said beam for sensing said beam and producing output detector signals whose amplitudes vary as a function of variations in the luminous intensity of the beam; circuit control means coupled to said photodetector means for processing said detector signals and counting the number of defects signified thereby above a selected threshold size responsive to the amplitudes of the detector signals including amplifier means for producing output signals upon occurrence of defects in the yarn sheet exceeding a selected defect size; a measuring roll and pulse generator means activated by contact with the yarns of said yarn sheet to produce pulses whose number is a measure of the travel of the yarn sheet, length function circuit means responsive to said pulses and to output signals from said amplifier means for counting the number of defects of selected size in the yarn passing through the beam during each selected length increment of the yarn sheet, and means for indicating occurrence at a selected number of defects counted by said length function circuit means during each said selected length increment.

24. Yarn inspecting apparatus as defined in claim 23, wherein said length function circuit means comprises first counter means responsive to said output signals for counting the number of defects signified by said output signals between successive resettings of said first counter means, and second counter means responsive to said pulses to count the same and reset said first counter means upon occurrence of a selected pulse count.

25. Yarn inspection apparatus for detecting slub-like defects in yarns forming a yarn sheet of plural substantially parallel yarns moving in a selected feed plane, comprising light source means located outwardly adjacent one edge of the yarn sheet for projecting light transversely across the yarn sheet in a narrow beam through which the yarns move, photodetector means located outwardly adjacent the opposite edge of the yarn sheet in the path of said beam for sensing said beam and producing output detector signals whose amplitudes vary as a function of variations in the luminous intensity of the beam; circuit control means coupled to said photodetector means for processing said detector signals including amplifier means for producing output signals upon occurrence of defects in the yarn sheet exceeding a selected defect size; a measuring roll and pulse generator means activated by contact with the yarns of said yarn sheet to produce pulses Whose number is a measure of the travel of the yarn sheet, length function circuit means responsive to said pulses and to output signals from said amplifier means for counting said pulses occurring during the period of each output signal from said amplifier means signifying a defect in the yarn passing through said beam, and means for indicating occurrence of defects of selected length sensed by said length function circuit means.

26. Yarn inspecting apparatus as defined in claim 25, wherein said length function circuit means comprises rst counter means responsive to said output signals for counting the number of pulses occurring during said output signals signifying the total length of defects between successive resettings of said rst counter means, and second counter means responsive to said pulses to count the same and reset said first counter means upon occurrence of a selected pulse count.

27. Yarn inspecting apparatus as defined in claim 24, including relay means for stopping feeding of the yarn sheet along said path, and switch means selectively connecting said relay means with said length function circuit means having a rst position disconnecting said relay means therefrom and a second position connecting the relay means therewith to activate the latter when the number of defects counted during any of said selected length increments exceeds a selected count level.

28. Yarn inspecting apparatus as defined in claim 26, including relay means for stopping feeding of the yarn sheetalong said path, and switch means selectively connecting said relay means with said length function circuit means having a first position disconnecting said relay means therefrom and a second position connecting the relay means to activate the latter When the total length of defects sensed during any of said selected length increments exceeds a selected length.

References Cited UNITED STATES PATENTS 3,030,853 4/1962 Strother Z50-219 X 3,124,289 3/1964 Lynch et al. 3,174,046 3/ 1965 Lindemann et al. 3,447,213 6/1969 Dost et al. 28-51 FOREIGN PATENTS 996,181 6/ 1965 Great Britain.

M. STEIN, Primary Examiner U.S. Cl. X.R. 

